(a) Field of the Invention
The field of the invention is built-in diagnostic tools for data processing systems and, more particularly, systems which verify with a high level of confidence the physical realization of the bus error detection and bus error recovery circuitry in a synchronous bus system.
(b) Description of the Background
Many newer data processing system architectures are distributed systems, consisting of a collection of several basic functional units. Each functional unit or module performs particular tasks required by the system. Examples of a functional unit are the circuitry for a general purpose processor, an I/O interface or a signal processor. Modules are interconnected in different ways to satisfy the specific requirements of a particular system application. Many applications interconnect modules, or a subset of the modules, in a system by means of a synchronous digital bus.
Reliable systems require complex, special purpose test circuitry and extensive diagnostic software to verify the operational error detection and error recovery logic circuitry on a module. Moreover, verification of this logic related to communication among modules via buses is critical for proper system operation following a bus failure. For instance, when a bus-related circuitry failure is detected on a module by diagnostic testing in a highly reliable, fault tolerant system, the module can be electrically isolated from the system bus and its task reassigned to another module.
Previous methods for testing transient failures in error detection and recovery logic test for each type of bus failure with logic and software dedicated to testing that specific bus failure. The normal operational circuitry and test software involved with bus error detection and recovery must necessarily be unique for each possible type of bus error, as dictated by a bus specification. However, the extensive, special-purpose test circuitry and diagnostic software to generate bus errors can be greatly reduced and replaced by a new methodology which provides a higher level of confidence testing.